Until Sunrise
by swallowedminds
Summary: Post ep for Cops and Robbers. For Valen. "He feels it too, that this thing between them, that whatever is holding them back isn't so strong here in this moment. And maybe, if they were alone, she'd drop her walls and let him in."
1. Chapter 1

**Post ep for Cops and Robbers.**

 **For Valen. Happy Birthday my dear friend. I love you and hope you have a beautiful day. :)**

* * *

The tips of his fingers have gone numb from nursing his cold drink, the semi-melted ice long since diluted the sting of alcohol. After Alexis retired to her room, his mother had brought out the harder liquor. Said something about feeling the burn of life.

All he feels is the burn of heartache.

He's sitting on the couch, trying to peel his eyes off of the woman giggling with his mother in the kitchen over a glass of red. Kate opted to keep her wine, already is two glasses in.

He loves seeing her so free. Loves knowing that she's comfortable enough in his home and with his family to let herself go.

She's all long legs and loose limbs, open laughter and flirtation. She's been teasing and baiting him all night. His mother has been enjoying the show, but Castle knows what's really going on, why Kate's letting herself open up when they've been trying to keep a lid on how they feel.

"Hey," she says sitting down beside him, hair in loose, wild waves around her face. She'd let the clip out and the remaining strands cascade down her shoulders. She kicks her heels off and curls her legs up on the couch beside him.

"Hey. You havin' fun over there?" he smiles, taking a sip of his drink, but then immediately regrets it.

"Yeah, your mom was telling me a story of when she was on Broadway. She's amazing, Castle."

"Don't I know it."

She takes another sip of wine and his eyes are drawn to her plush lips, extra pink from where her teeth keep sinking into them. He wants to reach out, touch his lips with hers with a desperation he hasn't felt since she woke up in the hospital. He almost _died_ and she saved his life.

 _Again_.

And he could see it in her eyes, that desire to throw caution to the wind and give into what she really wanted. Kate wants him. And it's taking every ounce of control he possesses not to lean in and lay his lips against her sweet ones, comb his fingers through her wild hair, and feel her heartbeat against his chest.

His heart is aching for her, every beat feels like it's trying to break free of his chest, and find its way to hers. And it hurts.

Loving her hurts.

"She was telling me about the time she played a 'Sinatra Concert' for an after party."

"Ahh, yes. I remember. I was shipped off to the neighbors, but I could still hear her playing the piano and singing for all the couples."

"And then you snuck over and thought I wouldn't notice," his mother interjects, sitting down on the opposite side of him.

"Come on, you had slipped in a Lennon song, how could I not?" he laughs and he finds Kate beaming along with him.

His chest contracts, his hands sliding closer to hers on the couch. In the back of his mind he wonders if his mother sees.

Kate's not looking down, is leaning forward to ask his mother a question, but she switches the wine glass to her right hand, her left coming to rest face up on the couch.

It's so high school, but the skin of his palm itches to slide against hers, kiss the veins that meander there, and entwine their fingers together.

Is it too much to ask for this agonizing wait to be over? He wishes for the love that comes from the playful touching and not this paralyzing uncertainty. He wishes they could skip this limbo and dive into the great unknown together.

He wishes for their happily ever after.

"Oh, my favorite Sinatra song to sing?" his mother repeats Kate's question and taps her fingers to her lips. "Hmmm. What's the one?"

Kate laughs at his mother's vague question.

"It goes like-" She proceeds to hum the tune, moves her hand in a wavy motion through the air to indicate the melody of the song. Castle's not paying attention though because he can feel the tip of Kate's pinkie against his palm.

He tries to keep his breathing under control, but soon she's got half her hand in his, her skin so soft as it brushes against him. He faces his mother, who's rising from the couch, but Kate has other ideas.

The entirety of her palm kisses his and his heart explodes in stardust at the contact.

Castle holds his breath and shuts his eyes when his mother sits at the piano. When she turns her back he lets his eyes travel to Kate. He's never seen her blush so hard before.

Her entire face is pink. She's looking down at her lap, using the wine glass to shield her nervous grin from him.

Adorable.

"Ahh of course, it's Fly Me to the Moon," he hears his mother answer in the background. But he pays her no mind.

He squeezes Kate's hand back, moves his body closer to hers on the couch until his thigh melts into her warm one. Castle wants to tuck her hair behind her ear but fears it may be too much for her to handle right now, but Kate continues to surprise him when she lifts her head, her eyes boring into his and her smile never wavering.

Her mouth opens, drawing his attention back to her lips, to speak, but no words come. Instead she swallows and leans her body forward; he can see her grip on the wine glass tighten.

She wants this just as bad as he does, and the thought is comforting. It's reassuring to know he's not the only one waiting for something.

"Richard," his mother calls before Kate can reach him. "Do you remember this song? Oh! I use to sing it all the time."

"How could I forget? You managed to perform it at junior prom." He doesn't let his gaze waver from Kate's, and she keeps hers on him too.

"Castle," she whispers almost imperceptibly and he nods in approval. He feels it too, that this thing between them, that whatever is holding them back isn't so strong here in this moment. And maybe, if they were alone, she'd drop her walls and let him in.

His mother sings the tune on the piano, and beckons him to come and join her.

"I know you know how to play it. I taught you the chords remember?"

He sighs and watches as Kate does too. His mother is two for two today.

Unhooking his hand from hers feels like ripping the skin off his body.

"I do remember the chords, mother," he says, rising from the couch. His mother continues to sing while he plays the song on the piano.

"Kate, darling, come join us!"

"Oh, Martha. I'm afraid I can't play." She's grinning when she walks over to lean against the piano, setting her wine glass down on top.

"No, sing, darling. Richard tells me you have an amazing voice."

Kate blushes even harder, and he's never seen such a beautiful sight so many times in one day. If she keeps taking his breath away like this, he isn't going to survive the evening.

" _Our life together is so precious together,_

 _We have grown - we have grown."_

Damn. Her voice is even sexier when she's loose, not feeling as self-conscious as other times she's sung in front of him. This is one of his favorite John Lennon songs and the way she sings it makes him fall in love with it all over again.

" _Although our love is still special,_

 _Let's take our chance and fly away somewhere alone."_

"I'm afraid," Kate begins, suddenly looking nervous. "That's all I know of the song."

He tries to mask his disappointment, but from the look she gives him she sees right through the facade.

"I'm just… more of a Sinatra fan. But I do like other classics."

"That's okay. I've got a good one I bet you'll love," his mother chimes in. She begins playing a song he's not familiar with, but from the way Beckett beams she must love it. It's slow enough to dance to so Castle reaches out his hand as he stands from the piano stool.

Kate panics for a moment, lips parting in surprise, until she swallows and slides her palm into his.

"Sing it in English dear," his mother smiles.

He leads her behind his mother so she won't feel watched, but he can tell from her stiff posture that she's nervous. He doesn't want her to be, so he grips her hand and twirls her around before pulling her into his chest. Kate laughs, shaking her head at him.

And then she starts to sing, managing to completely take his breath away at her beauty, her grace. He's mesmerized.

" _Hold me close and hold me fast_

 _This magic spell you cast_

 _This is la vie en rose."_

Castle can tell she's more accustomed to the French version from the way she sings it, her accent so prominent and precise that she could actually be singing in French and he would still be under her spell.

The song is somewhat playful; he remembers hearing it once or twice when he was younger but can't remember where.

He adds an extra skip in his steps while she sings, his arms around her waist tightening.

" _When you kiss me heaven sighs_

 _And though I close my eyes_

 _I see la vie en rose."_

He holds her eyes as they rock back and forth. He can see how difficult she's finding it, but she glances at him during the next verse, conjuring up images of a stolen kiss too long ago, only reminding him of how desperately he wants to repeat it.

" _When you press me to your heart_

 _I'm in a world apart_

 _A world where roses bloom."_

He twirls her, her hair fanning out like a dress, the scent of cherries wafting up to his nose. She giggles on "bloom" and tries to glare at him for making her mess up the high notes. But her arms come back and wrap around his neck, bringing their faces closer.

Without her heels, she's a head shorter than him, and he loves it. It gives him uninhibited access to her eyes, her face. He loves the mole lying just under her left lid, the touch of yellow in her irises. It's rare, these opportunities to see her so close, so open, and it makes him _feel_ closer to her, makes him wonder what the hell is stopping them from crossing this invisible line.

Castle leans his head down so his lips can caress her ear, his breath ghosting out across the skin there. "I like you like this," he whispers. He feels her breath hitch, her voice stuttering. She looks up at him as she continues to sing, voice getting softer now as she tries to trap the tentative smile that's begging to be set free.

" _And when you speak, angels sing from above._

 _Everyday words seem to turn into love songs."_

The song ends and she stops singing, her gaze still holding strong with his own. Eventually, their sway slows to a stop, but their hold on each other stays tight, as if each of them are afraid to let go, to break this spell her voice cast over them.

"Well, with that, I'm off to bed," his mother announces. "Katherine, you have a lovely voice. So sweet," she says, wrapping her arms around Kate's shoulders, unbinding their hold on each other.

Kate hugs her back and says goodnight, then his mother pulls him aside when she hugs him to whisper in his ear.

"You better kiss that girl."

He chuckles. "I plan on it."

His mother smiles before waving goodbye. "Don't stay up too late kids!"

And then, there were two.


	2. Chapter 2

There's only silence after Martha ascends the stairs.

She doesn't know what to say, how to approach Castle or this situation. All night she's wanted nothing more than alone time with him, to have a moment of vulnerability, but the right time just never arose. And now that it's finally here, Kate's not sure she can handle being alone with him anymore. She doesn't trust herself not to cross the invisible line she drew for them at the swings.

"Did I hear you say you don't know how to play?" Castle asks gesturing to the piano, walking by her to sit at the stool. The question eases some of the tension between them and she's grateful, can let her lungs expand.

"No, my dad tried to teach me for years, but I never really got the hang of it."

"I bet I could teach you in one night." He raises a brow in challenge, pats the part of the small stool next to him, beckoning her to sit.

Kate travels over, the bare pads of her feet silence her steps, but not the pounding of her heart. She can feel it in her palms, in her ears, her heart trying desperately to escape the confines of her chest that her whole body pulses with it. It wants Castle. And it's overwhelming how hard it is to keep denying her heart this simple pleasure.

Kate sucks in a deep breath and sits down.

"In one night? My dad's been trying to teach me for years, Castle. I don't think it's going to happen."

"Oh ye of little faith." He starts tapping a random melody on the keys, and she watches as his fingers move so effortlessly, one by one, striking the notes so they make a song. It's mesmerizing. And when she meets his eyes she finds his already watching her.

The spell could easily last the night, but Castle breaks it again with a question.

"What's _your_ favorite Sinatra song?" She opens her mouth but doesn't get a word out because he's speaking again. "Oh wait, no, lemme guess."

"That's a long shot, Castle," she says, smirking.

"Give me three guesses."

"And if you don't get it right?"

"I'll watch a Temptation Lane marathon with you," he answers, still working at the keys.

She laughs. "And if you do get it?"

"Maybe you put on a little concert for me."

She nudges his arm when he wiggles his eyebrow. "You aren't serious," she laughs.

"No, no. Maybe we watch Star Wars together? All of them. We can make a weekend thing."

"You're so on," she says, shaking her head.

"Ha! Okay, is this it?"

Castle begins to play a soft ballad, a slow melody mimicking Sinatra's _Moon Love_ , and as much as she loves this song, as many times as she's listened to this song and thought about _them_ , it's not her favorite one.

But it's almost like this could be their soundtrack tonight.

 _Say it's not moon love, tell me it's true love_

 _say you'll be mine when the moon disappears._

And Kate looks up out the window in front of them and remembers it's supposed to be a full moon tonight. It almost feels like fate.

"I love this, but no this is not my favorite," she says, turning back towards Castle. "Strike one."

"Fear not, I have two more tries. Now if this isn't it, I will definitely know which one it is."

Castle poises his fingers on the keys, wiggles his brow at her before pressing the keys.

"FLY ME TO THE MOON," he sings and Kate laughs, face turning red before she starts singing along with him.

"LET ME PLAY AMONG THE STARS," they sing together, both laughing at how ridiculous they sound. They calm down to their normal voices, but continue to sing a few lines of the song.

" _In other words, hold my hand. In other words, baby, kiss me."_

She catches his eye on kiss me, feels herself blush even deeper, and looks away to push her hair back behind her right ear, allowing the hair on her left to block her face from his view.

" _Fill my heart with song and let me sing forever more. You are all I long for, all I worship and adore."_

Castle's voice comes to a murmur, his playing to a stop, and she feels him turn towards her, his knee knocking into her thigh.

She doesn't see him lift his hand, but the next thing she knows he's pushing her hair from her face, and lifting her head to meet his eyes.

Kate sucks her lip between her teeth. She's trying to think of reasons why they shouldn't do this, why she shouldn't give her heart the desire it craves. But nothing comes.

Castle leans forward, the next lines of the song echo through the air, taunting them to the edge of this precipice.

"Castle," she whispers, her voice trembling.

He sighs, leans his forehead against hers. "Kate."

The hand on her cheek circles around her neck until it slowly descends down her collarbone, comes to rest just above the frantic beat of her heart.

She swallows, allows herself another few moments of him before she breaks the spell. She needs to go because she doesn't know what she'd do if this happened again tonight.

"That's not my favorite song."

He backs away from her confused. "Are you kidding me?"

"Not at all."

"I thought for sure I had that. I thought that was why…" he sighs, accepting the challenge is still on.

"Strike twooo," she sings, gaining her composure back. She watches his brow furrow as he stares at the black and white piano keys. "Would you like a hint?"

"No, no. I know what song it is."

"Really?" she smirks, folding her arms across her chest.

"Yeah, I'm just surprised, although I shouldn't be."

"Why?"

He faces her for a moment before he sets his fingers back in position on the keys. "You know what my favorite Sinatra song is?"

"Fly Me to the Moon?" she guesses. "Oh, no, wait. Is it Come Fly With Me? The Way You Look Tonight?"

Castle begins to tap one key on the piano, and Kate doesn't think anything of it, raises her brow in question.

"What's this?" she asks.

"My favorite," he answers, adding more notes and this is when she recognizes the song. _Her_ favorite song.

"This is...my-"

"Favorite song too? What a coincidence?"

 _I've got you under my skin_

 _I've got you deep in the heart of me_

 _So deep in my heart that you're really a part of me._

"You gonna teach me how to play it or what?" she asks, trying to avoid making the revelation any more astounding than what it is.

"Sure. So you know the notes right?"

"Yeah, the technical stuff I was able to learn, but it's physically playing that stumps me."

"Come a little closer," he says, relaxing his shoulders.

Kate scoots closer on the small bench until their thighs are in a complete embrace. "All right."

"Put your fingers on top of mine."

Her heart leaps. "What?"

"Put your fingers on top of mine. This is how my mother taught me and how I taught Alexis. Trust me, Kate. Just place your fingers on top of mine and try to follow them as I play, okay?"

Her lip finds its way back between her teeth as she nods, reaching over to place her fingers in position over Castle's thick digits.

She has to push her body even closer into his to do her left hand, his mouth so close to the side of her face Kate can feel him breathing.

"Ready?"

She nods.

Castle goes slow, but Kate follows his fingers with ease, notes every dip of his fingers as he presses the keys. She begins humming the song as Castle mutters which notes they're playing. She realizes there is a pattern to it, and beats Castle to some of the keys.

"Wanna do it again?" he asks, when they finish going through the first verse.

"Yeah, yeah."

They run through it again, this time with Castle humming the lyrics and Kate saying the notes. They go a tad faster than before and Kate laughs from excitement.

"That's amazing, Castle. Are you going to teach me the chorus?"

"Why don't you try it again by yourself and we'll see?"

Castle takes his hands off the keys and folds them in his lap.

"Are you sure?"

"I believe in you. Just focus."

If it was possible to make her more nervous he closes his eyes, preparing to listen to her play.

Kate lays her fingers out like Castle had them and flawlessly mimics the song. When she's finished the verse her jaw drops in surprise. Looking at Castle, she shouts her excitement.

"Oh my God, Castle!"

"I told you I could teach you."

"You are unbelievable." Kate looks down at her hands. "I can't believe I played that."

"Believe it," he says, and she can hear the smile in his voice. Kate slides her gaze back to his, finds his eyes beaming at her, the light in his eyes brighter as they glow from his uncapped love well.

"Thank yo-"

He interrupts her with a kiss.

He twines his fingers through her hair, pulls her closer into him, and she's surprised at first, but wastes no time melting into him.

Her arms wrap around his neck, her legs mushing against his until she's practically sitting in his lap. Her entire body shudders at the contact, from the way his hands cup her cheeks, the warmth from him seeps into her skin, lights her on fire.

Kate parts her lips, allows Castle access to her mouth, and he manages to have her body aching for more in seconds.

Electricity zips up her spine, forces her middle into Castle's where he's growing harder, thicker, pulsing with a desire that stems back years. And she's in no better shape.

He growls her name and it reverberates down her throat, bounces around in her heart, until she's a throbbing, mewling mess everywhere.

" _Castle_ ," she gasps, pushing away from him and standing from the bench. "We can't - I mean - we shouldn't - Castle I'm not -"

Kate can't get her thoughts straight. She's thinking so many things at once. And the one thing clouding her mind is how badly she wants to kiss him again, and he's just sitting there, hair ruffled looking so turned on and dumbfounded. And she just wants to kiss him better, but _damn it_ , her stupid heart isn't ready yet.

"I know," he finally says, when her throat begins to close up. Castle stands from the bench and the action makes the butterflies reappear in her stomach, sends them fluttering up her spine and down her legs. She leans into the piano for support. "I know you're not ready and that you're still working stuff out. I'm sorry, I never should've-"

"Please don't apologize."

"I just-"

Kate watches as he clenches his fists, his jaw tightening as if he has to physically stop himself from going to her. Her heart is beating out of control, and the air is too thick, making it harder to breathe. She feels everything so deeply and this thing between them is raw and...wet. She can't say no.

"Should I go?"

"No!" He lifts a hand to stop her from walking to the front door. "You don't have to go."

"It's probably best."

He takes a step closer.

She thinks her heart might be seconds away from bursting out of her chest.

He lowers his voice to a murmur, his tongue darting out to wet his lips.

"Or you could stay."

"Castle-"

"You've had two and half glasses of wine. You shouldn't be driving."

He takes another step closer until he's just a breath away, leans down so their foreheads are kissing.

"Rick," she whimpers, hands clinging to his forearms. And they stay like this for a few short moments, breathing each other in.

"Just stay," he whispers. "Stay until sunrise."

* * *

 _My deepest gratitude to Nushie, Amy, and Katherine for ther wonderful help and input. Thank you :)_

 _I hope you enjoyed, Valen! Happy Birthday._


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